The Sasanians were named for Sassan, a Persian high priest of Zoroastrianism. The Sassanids dominated southern Persia at first, but conquered the Parthian Empire in 224 and founded their own dynasty over Persia, rebuilding the empire that Darius III Codomannus had founded. By way of punitive expeditions, they defeated Arabic incursions into their land, and conquered the lands of northern India from the Rajputs, and also withstood several attacks by the Roman Emperor. King Shapur defeated Flavius Julianus at Ctesiphon in 363, costing the emperor his life, and routed a large Roman force, destroying the last attempt to invade Persia by the Eastern Roman Empire. Following this victory, Rome was forced to make peace and the Persians resorted to conquering their eastern enemies, the Khitans. There were still several wars with the Romans, and the Persians were victorious in the Iberian War in 531 after a victory at the Battle of Tricamarum, which led to a peace treaty with the Byzantine emperor Justinian I that led to the Persian recovery of all lands lost to the Byzantines. The Persians also fought the Byzantines in a war from 614 to 628, briefly seizing control of Jerusalem and Egypt. However, they were defeated at the Battle of Nineveh in 627 by Emperor Heraclius, and the Persians were forced to return their conquests to Byzantium. In 633 the Arabs of the Rashidun Caliphate invaded Persia during their quest to spread the word of Islam, and after the 641 AD Battle of Nahavand, the remnants of Persia's army were destroyed. By 654, the White Huns that supported Persia and the last few Persian nobles were conquered.